


Bones, Mostly.

by mockingbirdtank



Category: Undertale (Video Game)
Genre: Bondage, College Sucks, Dirty Talk, Eventual Smut, F/M, Reader Is Not Frisk, Reader has female parts, Slow Burn, Teacher-Student Relationship, author has gone mad with power, kind of, magic stuff, probs magic dick, skeleton sinning, there isn't much science
Language: English
Status: In-Progress
Published: 2016-02-01
Updated: 2016-02-01
Packaged: 2018-05-17 15:18:28
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 2
Words: 2,484
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/5875843
Author URL: https://archiveofourown.org/users/mockingbirdtank/pseuds/mockingbirdtank
Summary: <blockquote class="userstuff">
              <p>A few months have passed since the barrier between monsters and humans was shattered. You're a college student who was never good at science, much less biology, and having a magical, pun-cracking skeleton for a classmate does not exactly make things easier. But if it's science you struggle with, he'd be happy to tutor you. That is, when he's not busy teaching a class of his own, where all the students are from the underground. After all, human biology and monster biology are VERY different things...</p><p>This is the story of how you and Sans broke the universe.</p>
            </blockquote>





	1. Biology Sucks, for Real Though

**Author's Note:**

> Welp. You know what they say.
> 
> There's a first time for everything.

Who could ever really know how long humanity coexisted with the tendrils of magic right at their heels only a few miles underground? No, really, who could? Because time, a human concept, was exactly that to monsters. A _concept._ For these monsters were too busy making up their own rules to have time for a silly thing like…well, time.

You were a college student. Too young for misery yet too old for optimism. There could be paragraphs written about how special you were, complete with all your quirks in bulletpoints shaped like stars. But the fact remains…you were just another human on just another planet in just another solar system in just another galaxy. _Your_ galaxy, topsy-turvy as it was. You yourself were not a world, a thriving mass or wondrous anomaly of great importance. You were just…you. And that’s how it had always been.

Climbing the stairs unto the direction of your first class that dreary Monday morning seemed to turn the walls from gray to grayer. You were closing in on a new semester, and this class would last two hours at the maximum. That was only one; there were four others waiting in tow. Hell, your classes were a spinning universe of their own. Always changing, never quite stopping. It'd been that way since high school graduation.

There was something different this year, however. And no, it was not that the halls were missing their mingling scents of coffee and paperback textbooks priced something higher than what any student could afford.

No, it was not that there were suddenly posters strung up on the bulletin board with crude anime drawings inviting all passerby to join their club.

But in fact, it was that not too long ago, _they_ showed up.

Sprung up like flowers in a garden that didn’t have soil, leaving all of humanity mystified.

They, being-

“Psst!”

Your steps idled. You barely had time to turn the other way before you were shoved back playfully by someone you knew all too well.

“Hey stranger,” your friend Natalie greeted you, her toothy grin stretched from ear to ear. She looked just about as presentable as any other college attendee on the first day of school. But a week from then it would be sweatpants and band t-shirts galore. You’d seen it time and time again.

“Yo,” you threw back lazily. This humored her.

“Ah. So how’s that 8 AM treatin’ ya?”

The floaty smile on your face collapsed into a grimace. You caught yourself eyeing a clock on the wall off to the side.

“I still can’t believe I let you convince me to take a class _this_ early,” you said jokingly, yet unafraid to admit there was a bit of truth in your word. Natalie had swiveled to head for the door leading into room 204, casting a glance back your way.

“Well Y/N, I hate to be a bearer of bad news and all, but you can’t take all your classes after noon just so you can sleep in everyday.”

“Why not? I thought this was America.”

“Yeah but you’re a college student in America. There’s a distinction. You need to be more responsible with your schedule.”

You grumbled to yourself, unable to summon a witty retort as you both appeared outside the entryway. Your eyes, both slack with fatigue, swept a withering glare at the numbers encrypted before you. Two. Oh. Four.

“Did it _have_ to be Biology though?” you said the name as if it were unfathomably sour candy. Natalie snorted.

“Not my fault you waited so long to get your Science credits out of the way.”

“And yet here I am blaming you for it anyway.”

Because after all, it had been Natalie who insisted you take the class with her. A Biology class. At 8 AM. Mondays and Wednesdays. These were all things your heart insisted were wrong. _“But I can help you!”_ she had sworn. _“I’m really good at science!”_

And here she was parroting it back to you.

“I’m really good at science!” she batted her long lashes, feigning innocence. “Especially biology. You _know_ that. It's not like you'll have to struggle to get by or (gasp) learn everything all by yourself!”

“Sure, but what use is biology to us at this point in time?”

You swung so your back was facing the room as you carefully edged into it, whispering so that other students who were courteous and annoying enough to also show up half an hour before class, would not be disturbed.

Her manicured eyebrow quirked in that _what do you mean?_ sort of way.

“I mean with all the monsters out in the open now,” you paused, watching her eyes grow big at your mention of the M word.

“And with magic now butting its way into all our equations…”

She winced when you tacked on the _other_ M word, and you couldn’t help but smile at her reaction.

“Everything we know about biology could be totally wrong, you know?”

Elsewhere, someone was unafraid of speaking up.

“well. that’s an interesting way to look at it.”

Your shoulders had been passionately hunched, body language near theatrical until it pooled into something calm but not entirely collected. You spun to meet the eyes of whoever owned the voice that dared to chime in. It wasn’t just that it was unnaturally deep, and it wasn’t even what it had said. There was something different about it. It seemed foreign. _Alien._

And lo, you found the difference dead set before you, when you met eyes with something that in fact did not have eyes at all.

Nope, not an alien.

A skeleton.

He waved his skeleton hand at you.

“sorry. eavesdropping’s super rude, huh,” he said with his skeleton face, a.k.a. through two rows of teeth that were without lips, gum, or, from what you could see, a tongue of any sort. He was short in stature and wearing a blue parka, underneath which was a white shirt, and underneath _that_ he somehow was boasting a large-ish middle. Everything beneath his desk remained unseen and therefore, a mystery.

Your eyes grew wide. Your belongings almost slipped from your arms altogether.

Natalie voiced your concerns in perhaps the most abrasive way possible.

“Holy shit a MONSTER.”


	2. Your Friend's Choices Lead to a Bad Pick-Up Line.

**Notes for the Chapter:**

> And this is where it all begins.

Normally you would have thought it fair to nudge your friend and tell her to maybe not, erm, call monsters… _monsters._  At least not to their face. It had been a few months since they emerged from underground and spilled into the streets of towns all over, like a tipped over jar of candy. The reception to them had been a not-so healthy blend of both adoration and hatred. It was easy to call anyone who didn’t take well to them bigots. Correlating to such, it made no sense to call them by their species. It made them seem lesser than humans. Almost as though they were objects.

But this skeleton seemed to have no qualms with such greeting at all, and Natalie was suddenly upon him, having abandoned you at the door like chopped liver.

“What’s your name?!” she exclaimed. The monster, no, skeleton, beamed up at her, throwing his arms behind his head and lounging.

“i’m sans. sans the skeleton.”

The name flapped about in your head. Not with wings. It wore something less graceful.

_Sans…_

Just like…

“The font?” you breathed the words out into the open without meaning to. Sans looked past Natalie and directly at you. Indeed, he had no eyes, but his sockets were not entirely empty. Within the black voids, there were a pair of orbs acting as pupils. They settled on you then, and boy did it make you want to shiver. Was it wrong to call it a little scary?

“mad props, kiddo. you’re like the hundredth person to point that out,” he snickered. Immediately the awe washed away to unveil something nastier underneath. Your brows narrowed.

Was he making fun of you?

And did he just call you _kiddo?_

You could’ve sworn he winked at you (with WHAT? Skeletons don’t have eyelids!) before Natalie leaned onto his desk, mouth hanging open in glee.

“Woah...you’re really cool!” she blurted, to which you almost groaned from the foreground before awkwardly scoping out a seat to claim. Your bags were too heavy to just stand there and perpetuate that whole _staring_ thing.

And just as you went to pick a perfectly charming spot by the window, near a fish bowl chock-full of baby turtles, you felt your collar snatched and pulled back so far it nearly asphyxiated you.

“Do you mind if we sit by you, Sans? I have so many questions about the Underground! I-If that’s okay! Please tell me if I’m being annoying!”

“You’re being annoying,” you growled as the shorter, curly-haired woman dragged you back into the skeleton’s vicinity. She turned to throw you a frown, but Sans was already chortling in a view peeking just beyond her shoulder.

“no gripes here. you guys are pretty hilarious. and comin' from me, that means somethin',” Sans drummed his bony fingers on the tabletop, shrugging to himself, while wearing a grin somehow larger than the last. Natalie very loudly took the seat to his left while you stumbled out of her grasp and seated yourself directly in front of him. You cringed as you heard the familiar squeak of metal on tile floor as Natalie dragged her desk closer to touch his.

“I think monsters are super cool! I have since the beginning!” she announced for all the world to hear. “I’ve seen plenty of them at the mall, and the supermarket and restaurants and even a few parties but I’ve never gotten the chance to really _talk_ to one!”

“hm, that's strange,” Sans noted from behind you. “i'd think it would be easy to cross paths with the likes of us since we’re always _butting in with our magic.”_

You couldn’t find the nerve to turn around and look at him. He sounded far too close, and you knew for certain now that he was making fun of you. Your face burned with frustration, and an added vial of pink from embarrassment. You pretended to be super interested in the rest of the students filing into the classroom, all human of course. Though this was mostly a lost cause because A) Natalie was super fucking loud and B) anyone coming into class immediately noticed Sans and fell headfirst into perplexed nervousness. And also C) Sans was indeed right behind you. Like _right_ behind you. If you concentrated hard enough, you could hear him breathing.

But skeletons don’t have respiratory systems!?

“Don’t mind her,” Natalie waved you aside. “She’s not a hater or anything. I think she’s just cranky because it’s too early in the morning for her.”

“well, can’t say i blame her,” you felt the crashing weight of sans’ shoes on the basket beneath your desk, using them as support, and cringed. “not much of an early riser myself.”

“Oh my god no way!” Natalie gasped. “So you _can_ sleep! How cool! Do you dream, too?”

“sure i dream. if i’m asleep for long enough.”

Natalie was dazzled, to say the least.

“What do you dream about?”

This was getting real invasive, real fast.

“bones, mostly.”

Bones…mostly?

“You-…huh?” the enthusiasm dressing Natalie’s expression died into quiet embers. He had stumped her, and apparently for this he felt victorious. The next thing to come from him was a satisfied chuckle.

“that was supposed to be a joke. but I uh, guess it was a bad one.”

You could feel the swell of Natalie’s interjection as she was ready to swear his joke wasn’t bad, that it was perfect and that everything about him and monsters was perfect, until he said,

“maybe i should _give it a rest.”_

You couldn’t help it. You snorted before you had time to even think about what you were doing, and the implication it carried. Natalie stared between both of you dumbfounded before it dawned on her as well. She laughed like she had never laughed before.

He was a skeleton. A monster skeleton. He could sleep, dream, and most importantly he knew how to make puns.

What was happening to the world.

“oh, didya like that one?” Sans asked, and to whom it was directed was not entirely clear. “i was going to make a joke about a mattress too, but then i decided to _sleep on it.”_

If Natalie didn’t have any dignity about her she probably would have let herself crumble to the floor in a fit of giggles. But for now, doubling over in her chair while choking on her bubblegum would have to suffice.

You, however, impressed as you were, did not say a word, and even tried your best not to make a sound. You wouldn’t let him have that victory. Quietly, you pried your textbook out from your bag, placing it with an unceremonious _thud_ on your desk. Pending the sound, Natalie sucked in a pocket of air, and suddenly the sound of her jewelry clinging together went off like glitter next to you.

“Shit, I remembered to bring everything but my biology textbook!”

Well that was impressive.

Deciding it would be a dick move to ignore her, you looked over her way quizzically. “Where is it, then?”

“I left it in my car!”

“Oh Natalie for the love of-“

“Howdy, class! How is everyone today?”

Your professor had only just made an entry when Natalie bolted past him. Remaining passive, the elderly man didn’t even grace her momentary presence with any attention whatsoever. He moved to the chalkboard to write out his name.

“I am Professor Yomosob! Surely you already read that on your online syllabus and _yes_ it's a funny name…”

Anything he said afterward went through you like a phantom the moment two fingers tapped you on the spine.

Against better judgment, you turned around, slightly annoyed but mostly docile, to face the skeleton head on. Alone. Without Natalie as a distraction to either of you. Maybe he needed a pencil?

That’s when all thoughts turned to dust upon realizing, truly, how close he was. Those specks of white were goddamn constellations. His skull had pits and grooves about it, as if he’d been around a long time. You had almost lost yourself when his already permanent smile fluctuated to produce something even wider.

“say kiddo, you sure we’re taking biology?”

Words melted on your tongue when you noticed out the corner of your eye, your professor was wheeling a plastic skeleton on a hook toward the corner of the room. It was awfully cheap looking and labeled by notecards. In poor taste, no doubt.

And then the monster's voice was right at your ear.

“because with you here, this feels more like _chemistry.”_

 

 

 

 

 

 

 


End file.
